Process for producing 1, 3-propanediol

ABSTRACT

Disclosed herein are processes for the recovery of 1,3-propanediol from an aqueous feed stream. The present invention involves contacting an aqueous feed stream that comprises water, 1,3-propanediol, and at least one contaminant with at least one solvent extractant to form a mixture. The mixture is separated into a first phase and a second phase. The second phase comprises a majority of the water from the aqueous feed stream. The first phase comprises solvent extractant and at least some of the 1,3-propanediol that was present in the aqueous feed stream. The weight ratio in the first phase of 1,3-propanediol to any one contaminant present is greater than the weight ratio of 1,3-propanediol to the same contaminant in the aqueous feed stream prior to the aqueous feed stream being contacted with the solvent extractant. The first phase can be removed from the separated second phase in order to recover the 1,3-propanediol.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to processes forproducing and recovering 1,3-propanediol. More particularly, it concernsmethods that rely on solvent extraction for production and recovery of1,3-propanediol.

[0003] 2. Description of Related Art

[0004] Purified 1,3-propanediol (PDO) can be produced commercially bymethods known in the art that can involve fermentation, chemical, andmechanical separation processes. It is possible to produce1,3-propanediol by fermentation, and production in this way requiresmethods of purifying 1,3-propanediol by targeting the removal ofimpurities that are the result of fermentation. When PDO is produced byfermentation the broth can contain a number of compounds such asglycerol and 1,2,4-butanetriol, which are very similar in chemicalcomposition and properties to PDO. Glucose, a material that can be usedto feed fermentation, is a compound that also has similarities to1,3-propanediol, and residual amounts of glucose can remain afterfermentation. A disadvantage of the fermentation route using glucose forthe production of 1,3-propanediol is that sugars such as glucose willcreate color in downstream processes involving heat, such asdistillation and evaporation. Preferably the residual glucose isseparated from the PDO to purify the PDO. There is a need for a processto separate 1,3-propanediol from impurities in addition to sugars thatwill result in greater purity of the PDO, and that can eliminate orreduce the amount of energy intensive distillation (e.g., a commonmethod of purifying PDO) required to produce the purified PDO.

SUMMARY OF THE INVENTION

[0005] Certain embodiments of the present invention are directed toprocesses for the recovery of 1,3-propanediol from an aqueous feedstream. The aqueous feed stream comprises water, 1,3-propanediol and atleast one contaminant. Preferably the aqueous feed stream comprises afermentation broth that is concentrated and/or partially purified. Incertain preferred embodiments, the aqueous feed stream comprises betweenabout 5 wt % to 85 wt % 1,3-propanediol, and further comprises greaterthan about 10 wt % water, and between about 5 wt % to 70 wt % of one ormore of the contaminants. In certain embodiments, the aqueous feedstream comprises up to 90 wt % dry solids. Preferably the feed streamcomprises between about 20 wt % and 80 wt % dry solids. The at least onecontaminant present in the aqueous feed stream is preferably a compoundselected from the group consisting of organic acids, organic salts,inorganic salts, carbohydrates, alcohols, proteins, amino acids, and lowmolecular weight hydroxylated compounds. A low molecular weighthydroxylated compound can be selected from the group consisting ofglycerol, glucose, and butanetriol. Preferably the aqueous feed streamhas a pH of between about 2 and 11, more preferably between about 6 and8.

[0006] The aqueous feed stream is contacted with at least one solventextractant to form a first mixture. The contacting of the solventextractant and the aqueous feed stream can be performed counter current,cross current, or counter cross current, as explained below. Thecontacting can be performed using more than one stage, as is known inthe art for the contacting of two liquids. In certain embodiments thesolvent extractant is essentially anhydrous (e.g., comprising less thanabout 0.5 wt % water), and in others it is saturated with water.Preferably the at least one solvent extractant is selected from thegroup consisting of alcohols, ketones, esters, acids, ethers orvegetable oils with hydrophobic parameter logP(logP=[solute]octanol/[solute]water) of between about 0.8 and 7.7. Incertain preferred embodiments the solvent extractant has a hydrophobicparameter of between about 0.8 and 2.9. (Biotechnology andBioengineering Vol. 30, pages 81-87, July 1987; Biotechnol. Prog., Vol.7 No. 2) In certain embodiments the solvent extractant is selected fromthe group consisting of (1) alkanols such as pentanol, propan-1-ol,hexanol, or oleyl alcohol, (2) ketones like 4-methyl pentan-2-one, (3)esters like isopropyl acetate or tributyl phosphate, (4) acids likeoleic acid (5) oils like soya oil, or castor oil, and (6) ethers.Preferably the solvent extractant is hexanol or tributylphosphate. Incertain embodiments the solvent extractant has a carbon to oxygen atomratio of between about 2:1 and 18:1, more preferably 2:1 and 10:1 andmost preferably 3:1 and 6:1.

[0007] In certain embodiments a phase enhancer selected from aliphaticand aromatic hydrocarbons can be used in addition to solvent extractants(such as those taught above) in order to enhance phase separation.Preferred phase enhancers are alkanes in the range from hexane to decane(e.g., having from 6 to nine carbon atoms).

[0008] The first mixture is separated into a first phase and a secondphase. The first phase comprises a majority (e.g., greater than about50%) of the solvent extractant and at least some of the 1,3-propanediolthat was present in the aqueous feed stream. The weight ratio in thefirst phase of 1,3-propanediol to any one contaminant present is greaterthan the weight ratio of 1,3-propanediol to the same contaminant in theaqueous feed stream prior to the aqueous feed stream being contactedwith the solvent extractant. Thus, the 1,3-propanediol in the firstphase is purer than the 1,3-propanediol in the aqueous feed stream. Thesecond phase comprises a majority (e.g., greater than about 50 wt %) ofthe water from the aqueous feed stream, and at least some of thecontaminant from the aqueous feed stream. The separation can beperformed using methods known in the art. In certain embodiments, thecontacting step and separation of the first phase and the second phaseare carried out in a mixer-settler. In certain preferred embodiments thefirst phase is separated from the second phase using a centrifuge. Incertain embodiments purified 1,3-propanediol is recovered by removingthe first phase from the second phase. Certain embodiments of thepresent invention are preferably carried out a temperature between about20° C. and 90° C., more preferably between about 25° C. and 35° C., andmost preferably at a temperature of about 30° C.

[0009] In certain embodiments, the removed first phase is contacted witha first quantity of aqueous solution or water to form a second mixture.The volume ratio of the first quantity of water or aqueous solution tothe first phase is between about 20:1 and 1:20, more preferably betweenabout 20:1 and 1:1, and most preferably about 7:1 and 3:1. The secondmixture is separated into a third phase and a fourth phase. The thirdphase comprises a majority (e.g., greater than about 50 wt %) of solventextractant of the first phase. The fourth phase comprises1,3-propanediol and a majority (e.g., greater than about 50 wt %) of thefirst quantity of aqueous solution or water. The weight ratio in thefourth phase of 1,3-propanediol to any one contaminant present isgreater than the weight ratio of 1,3-propanediol to the same contaminantin the aqueous feed stream prior to the aqueous feed stream beingcontacted with the solvent extractant. Thus, the 1,3-propanediol in thefourth phase is purer than the 1,3-propanediol in the aqueous feedstream. The separation can be performed using methods known in the artfor separation of two immiscible or partially miscible liquids. Incertain embodiments purified 1,3-propanediol is recovered by removing(e.g., by decantation) the fourth phase from the third phase. In certainembodiments, the recovered third phase can be recycled to the solventextractant used in the first mixture. The recovered fourth phase can betreated to further purify the 1,3-propanediol in the fourth phase. Thefourth phase can be recycled such that the aqueous feed stream for thefirst mixture comprises the recovered fourth phase.

[0010] In certain embodiments, the removed first phase further comprisesat least some water in addition to the 1,3-propanediol and solventextractant, and the removed first phase is contacted with a hydrophobicsolvent to form a second mixture. Preferably the weight ratio of theremoved first phase to the hydrophobic solvent in the second mixture isbetween about 4:1 to 1:4, preferably 2:1 to 1:2. Preferably thehydrophobic solvent is selected from solvents with logP of between about3.0 and 10, preferably 3.5 to 5.5. Preferably the hydrophobic solvent isselected from alkanes in the range having molecular weights betweenhexane and that of dodecane. The second mixture is separated into athird phase and a fourth phase. The third phase comprises the majority(e.g., greater than about 50 wt %) of both the solvent extractant andthe hydrophobic solvent of the second mixture. The fourth phasecomprises 1,3-propanediol and the majority (e.g., greater than about 50wt %) of the water of the first phase. Preferably the weight ratio inthe fourth phase of the 1,3-propanediol to any one contaminant presentis greater than the weight ratio of the 1,3-propanediol to the samecontaminant in the aqueous feed stream prior to the aqueous feed streambeing contacted with the solvent extractant. Thus, the 1,3-propanediolin the fourth phase is purer than the 1,3-propanediol in the aqueousfeed stream. The 1,3-propanediol can be recovered by removing the fourthphase from the third phase.

[0011] Certain processes of the present invention involve adjusting thetemperature of the first mixture during the contacting step such that1,3-propanediol is more soluble in the solvent extractant than in theaqueous feed stream and the solvent extractant is hexanol. The firstmixture of the aqueous feed stream and the solvent extractant isseparated into the first phase and the second phase, as described above.The first phase is removed from the second phase. The temperature of thefirst phase is adjusted such that a second mixture is formed. The secondmixture is separated into a third phase and a fourth phase. The thirdphase comprises a majority of the hexanol from the first phase, and thefourth phase comprises 1,3-propanediol. Preferably the weight ratio inthe fourth phase of 1,3-propanediol to any one contaminant present isgreater than the weight ratio of 1,3-propanediol to the same contaminantin the aqueous feed stream prior to the aqueous feed stream beingcontacted with the solvent extractant.

[0012] Certain methods known in the art for purification of PDO from anaqueous feed (i.e., fermentation broth) comprising contaminants involveextracting contaminants while leaving the PDO in the aqueous feedstream. Certain methods of the present invention involve extracting thePDO from the aqueous feed stream, into a solvent phase away fromcontaminants present in the feed. Certain embodiments of the presentinvention can increase the purity of 1,3-propanediol from impure feedstreams.

BRIEF DESCRIPTION OF FIGURES

[0013]FIG. 1 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol.

[0014]FIG. 2 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol with back extraction involvingwater.

[0015]FIG. 3 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol with back extraction involvinga hydrophobic solvent.

[0016]FIG. 4 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol with back extraction involvinga change in temperature.

[0017]FIG. 5 is a process flow diagram of cross current contacting of afeed stream and a solvent extractant for extraction of 1,3-propanediol.

[0018]FIG. 6 is a process flow diagram of counter current contacting ofa feed stream and a solvent extractant for extraction of1,3-propanediol.

[0019]FIG. 7 is a process flow diagram of counter cross currentcontacting of a feed stream and a solvent extractant for extraction of1,3-propanediol.

[0020]FIG. 8 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol.

[0021]FIG. 9 is a process flow diagram in accordance with the presentinvention for recovery of 1,3-propanediol involving a washing process.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0022]FIG. 1 is a schematic of a process of the present invention. Anaqueous feed stream (e.g., a fermentation broth) 14 comprising water,1,3-propanediol and at least one contaminant is contacted with solventextractant 10 in an extractor 12 to form a first mixture. The solventextractant is preferably immiscible or partially miscible with waterover a range of temperatures (e.g., 2° C. and 100° C.). Thevolume/volume ratio of solvent extractant 10 to aqueous feed stream 14(e.g., filtered fermentation broth, as described below) is preferablybetween 1:4 and 50:1, more preferably about 10:1. In certain preferredembodiments the solvent extractant has a hydrophobic parameter logP(logP=[solute]octanol/[solute]water) of between about 0.8 and 7.7, andmore preferably 0.8 and 2.9 such as those listed in the table below. Apreferred solvent extractant is tri-butyl phosphate (TBP). ethyl acetate0.68 propyl acetate 1.2 hexanol 1.8 TBP 2.0 (estimated) heptanol 2.4octanol 2.8

[0023] The aqueous 1,3-propanediol feed stream 14 and the solventextractant (e.g., TBP) 10 are agitated at a temperature between about 2°C. and 100° C., more preferably 30° C. After agitation the combinedmixture can be allowed to settle and separate into two phases. A firstphase 16 comprises a majority (e.g., greater than about 50 wt %) of thesolvent extractant, and a second phase 18 comprises a majority (e.g.,greater than about 50 wt %) of the water present in the first mixture12. The first phase comprises at least some of the 1,3-propanediol thatwas present in the aqueous feed stream 14 and the weight ratio of the1,3-propanediol to any one contaminant present in the first phase isgreater than the weight ratio of the 1,3-propanediol to the samecontaminant in the aqueous feed stream 14 prior to the aqueous feedstream being contacted with the solvent extractant 10. The first phase16 can be separated and removed from the second phase 18 to recover1,3-propanediol by methods known in the art (e.g., centrifugation anddecantation, among others.) The recovered 1,3-propanediol is purer(e.g., have relatively less contaminant per amount of 1,3-propanediolpresent) than the starting aqueous feed stream.

[0024] The first phase 16 comprises 1,3-propanediol and solventextractant, and the majority (e.g., greater than about 50 wt %) of the1,3-propanediol can be transferred back (e.g., back extracted) to anenriched aqueous phase by several methods. The back extraction processcan in certain embodiments involve known mixer-settler systems orcentrifugal systems. Back extraction can be accomplished by severalmethods. These include use of water or aqueous solution (FIG. 2), use ofa second solvent that is hydrophobic (FIG. 3), or use of a change intemperature (FIG. 4).

[0025] Back extraction with water or an aqueous solution is shown inFIG. 2. A first quantity of water or aqueous solution 26 is contactedwith a first phase 16, as described above to form a second mixture 22.The first quantity of water 26 can be contacted with the first phase 16at a range of temperatures from about 2° C. to 100° C., preferably 30°C. The first quantity of water 26 to first phase 16 can be between about20:1 to 1:20 v/v, but is preferably about 3:1 v/v. At least some of the1,3-propanediol transfers from the first phase 16 to a fourth aqueousphase 28, and this can be removed, for example, from a settler bydecantation leaving a third solvent extractant phase 24, which can berecycled for further extraction processes (e.g., recycled to solventextractant). The third phase 24 comprises a majority (e.g., greater thanabout 50 wt %) of the solvent extractant from the second mixture. Thefourth phase 28 comprises a majority (e.g., greater than about 50 wt %)of the water from the second mixture. In certain embodiments, acentrifuge can also be used to separate the aqueous phase 28 from thesolvent extractant phase 24. The weight ratio in the fourth phase 28 ofthe 1,3-propanediol to any one contaminant present is greater than theweight ratio of 1,3-propanediol to the same contaminant in the aqueousfeed stream prior to the aqueous feed stream being contacted with thesolvent extractant.

[0026] An alternate way of accomplishing back extraction is with ahydrophobic solvent, and this is shown in FIG. 3. Preferably thehydrophobic solvent is selected from solvents with logP of between about3.0 and 5.5, such as those in the table below. Preferred hydrophobicsolvents are alkanes in the range from hexane to decane. decanol 4.0dodecanol 5.0 hexane 3.5 heptane 4.0 octane 4.5 decane 5.98 Soy oil 7.4

[0027] The first phase 16 comprising 1,3-propanediol, solventextractant, and at least some water can be contacted with a hydrophobicsolvent 36 (e.g., hexane) to form a second mixture 32, and the mixture32 can be allowed to settle to form two phases. The contacting andsettling can be performed in mixer-settler equipment. In certainembodiments, the two phases can be separated in a centrifugal device.One of the two phases is a solvent phase 34 comprising a majority (e.g.,greater than about 50 wt %) of the solvent extractant and thehydrophobic solvent, and the other phase is an aqueous phase 38 enrichedin 1,3-propanediol that was transferred from the first phase 16. Theaqueous phase 38 is comprised of a majority of the water (e.g., greaterthan about 50 wt %) and 1,3-propanediol that was present in the firstphase 16. A preferred ratio of first phase 16 to hydrophobic solvent 36is between about 4:1 and 1:4, more preferably between about 2:1 and 1:2,in the back extraction with the hydrophobic solvent.

[0028] A third way of releasing the 1,3-propanediol from the solvent canbe accomplished by extracting, and back extracting at differenttemperatures (FIG. 4). This can be done using, for example, hexanol as asolvent extractant 44. The aqueous feed 40 is brought into contact withhexanol at about 80° C. in a mixer-settler 42, and upon settling theaqueous phase 46 (e.g., comprising water from the aqueous feed stream)with the impurities is discarded. The hexanol/1,3-propanediol mixture 45that is removed at 80° C. is cooled to about 30° C., whereupon thematerial will separate into two phases in the back extractor 48. Onephase 50 comprises hexanol and can be recycled. The other phase 52comprises water, and is enriched in 1,3-propanediol. A preferred weightratio of aqueous feed at 30% d.s. to hexanol solvent would be about 1:3

[0029] The processes depicted in FIGS. 1 through 4 can increase thepropane-1,3-diol content of a fermentation broth or other aqueous feedstream, calculated on a water-free basis, from about 85% to over 99% byweight, and the 1,3-propanediol can be much purer than in the startingfeed stream.

[0030] The contacting of the 1,3-propanediol and the solvent can becarried out in one stage, or in multiple stages. Treatment with a numberof stages (e.g., from 1 to n) increases the effectiveness of thetransfer of the 1,3-propanediol from one phase to the other phase. Thereare a number of ways of using multiple stages. For example, across-current arrangement set up (FIG. 5), as is known in the art, canbe used for an extraction. There can be any number of stages from 1 to nwith each stage representing mixing and separation (e.g., mixersettlers, 204-1, 204-2, 204-3, 204-n). Fresh solvent extractant 202 isfed into each stage 204-1, 204-2, 204-3, 204-n, whereas the feedmaterial 200 containing 1,3-propanediol passes through each stage 204-1,204-2, 204-3, 204-n in turn. In each stage there are two phases and thefraction with solvent containing 1,3-propanediol (e.g., first phase 206)can be removed at each stage. Usually these fractions can be combined.Each stage can be provided with the means for internal recycle of thesolvent extractant 202 or the second phase 208 so that the proportion ofthe phases can be optimized for coalescence and separationcharacteristics.

[0031] Alternatively a counter-current arrangement (FIG. 6), as is knownin the art, can be used for extraction. This can have any number ofstages from 1 to n, and each stage represents mixing and separation(e.g., mixer settlers, 204-1, 204-2, 204-3, 204-n). The aqueous feed 200containing 1,3-propanediol and the solvent extractant 202 are passed inopposite directions through the stages 204-1, 204-2, 204-3, 204-n, withthe depleted feed (e.g., second phase 208) leaving the last stage 204-n,and the first phase 206 leaving stage 204-1. Also in this configurationeach stage 204-1, 204-2, 204-3, 204-n can be provided with the means forinternal recycle of the solvent extractant 202 or the second phase 208so that the proportion of the phases can be optimized for coalescenceand separation characteristics.

[0032] Another possible method of extraction can involve counter crosscurrent (as is known in the art, FIG. 7) of the aqueous feed stream 200and the solvent extractant 202. In this method, fresh solvent extractant202 can be added into any of the stages 1 to n 204-1, 204-2, 204-3,204-n, but the first phase 206 is passed counter-current from stage204-n and withdrawn at stage 204-1, with the depleted feed (e.g., secondphase 208) leaving the last stage n.

[0033]FIG. 8 is a more detailed schematic of a process of the presentinvention. A fermentation broth produced by fermentation or otheraqueous feed comprising 1,3-propanediol 110 comprises at least onecontaminant that can be selected from organic acids or salts thereof,inorganic salts, protein fragments, ketones, metal ions, cells, cellulardebris, fermentation products (e.g., glycerol, and 1,2,4-butanetriol,among others), color impurities, water, nutrients (e.g., ammonia andphosphate, among others), and unused carbon source (e.g., glucose). Afermentation seed stock can be generated using a fermentation seedtrain. The fermentation seed stock is introduced into a fermentation forthe production of 1,3-propanediol, along with fresh nutrients, water,and a carbon source. Methods of fermentation are known in the art. Thecell culture is then processed to recover the fermentation broth 110.The present invention provides means for recovering 1,3-propanediol fromfermentation broth. However, it should be understood that the presentinvention is not limited to use in conjunction with fermentation, nor isit limited to use with broth that has been purified, and/orconcentrated, as pointed out below.

[0034] Preferably at least about 75 wt % of the solids (e.g., cells andcellular debris) in the fermentation broth 110 are removed by filtrationor centrifugation methods 120 known in the art (e.g., rotary vacuumfilter or vacuum belt filter). More preferably at least about 90 wt % ofthe solids in the fermentation broth 110 are removed, most preferably atleast about 95 wt %. The dry solids content of the filtered fermentationbroth is preferably between about 8 and 20% dry solids (d.s.), morepreferably about 15% on a dry solids basis. The filtered fermentationbroth 120 can optionally be concentrated by removal of water in anevaporator 130, resulting in a broth preferably having 30 to 50% d.s.,more preferably about 40% d.s.

[0035] The fermentation broth 110, 120 can undergo partial purificationand/or pre-treatment prior to recovery of 1,3-propanediol using methodsknown in the art. Partial purification can, for example, compriseprecipitation and removal of certain impurities.

[0036] A solvent extractant 132 comprising one or more solvents can becontacted in an extractor 140 with the filtered and optionallyconcentrated fermentation broth 130. One preferred solvent extractant istri-butyl phosphate (TBP). The solvent extractor 140 can be in a numberof stages using counter-current flow, counter cross-current flow,cross-current flow, mixer-settlers or centrifugal contacting devices, orother devices commonly used for liquid-liquid extraction. The extractionsystem 140 can be just one stage, but for efficient operation givinggood yield it is preferable to use multiple stages. A typical ratio offeed (e.g., filtered and optionally concentrated fermentation broth) at40% d.s. to solvent extractant used in extraction is about 1:10.

[0037] The second phase 141 comprising water will comprise most of thesugars, salts and at least some of the glycerol and other impuritiesthat were present in the filtered broth 130. The sugars, salt andglycerol (e.g., raffinate) can be discarded 141, or purified further ifdesired.

[0038] The first phase 142 comprising the solvent extractant comprises1,3-propanediol, extracted from the feed stream 130 by the solvent(preferably TBP) along with some of the impurities present in theaqueous feed stream 130. This can be purified further in a purificationextractor 150 by using a wash with a limited quantity of aqueoussolution or water 151. Optionally, the aqueous solution 151 can comprisea dilute base such as caustic soda, to remove some color and organicacids from the first phase 142. The quantity of water or dilute base(e.g., aqueous solution) used at this stage is typically at a ratio tothe first phase of 1:15, but is always less than the amount used in theback-extraction 160. The aqueous phase 152 from the purificationextractor 150, which is a stream containing the washings from thepurification stage, can be mixed with the solvent extractant 132. Thepurpose of the purification step 150 is to wash the remaining impuritiesfrom the first phase, giving a high degree of purification. Theimpurities will contain some 1,3-propanediol, but this can be recoveredwhen the washings 152 are recycled to the extraction step 140.

[0039] The purification extractor 150 is a liquid-liquid extraction unitand can be, for example, mixer-settlers or centrifugal contactors. Thenumber can range from one to multiple units, depending on theeffectiveness of purification required.

[0040] The purified 1,3-propanediol in the solvent extractant (such asTBP), 153, is termed the purified first phase and comprises solventextractant. The next step is to send the purified first phase 153 to aback extraction unit 160. This unit applies water 161 in sufficientquantity to transfer the 1,3-propanediol from the purified first phase153 into the water phase 163. The back extractor 160 is preferably aliquid-liquid contacting unit, and can be a mixer-settler, a columnextractor, or a centrifugal contacting device, for example. There can beone stage or multiple stages depending on the effectiveness ofback-extraction required. The ratio of water 161 to purified first phase153 is preferably 1:4. The 1,3-propanediol is transferred to the heavy,aqueous phase 163. The stream comprising solvent extractant (e.g., TBP)162 from the back extraction unit 160, can be recycled to the extractionunit 140. Optionally, the water can be removed from this solventextractant stream 162 by distillation 172, and the water 173 discarded.About 6% water can dissolve in TBP (e.g., solvent extractant) at certaintemperatures used, and removal of this water 173 to get dehydratedsolvent extractant can improve the effectiveness of extraction in theextractor 140.

[0041] TBP that can be used in the present invention is partiallysoluble in water. The remaining solvent can be removed from the aqueousstream 163 that contains purified 1,3-propanediol by treatment with ahydrophobic solvent 164, such as hexane, in a liquid-liquid extractionstripper unit 165. The hydrophobic solvent stream 164 (e.g., hexane)will separate solvent extractant from the water, leaving the1,3-propanediol in water with virtually no dissolved or entrainedsolvent extractant. This stripper 165 can be a mixer-settler or acentrifugal contactor, and there can be one or multiple stages,depending on the effectiveness required. The typical ratio of aqueousproduct stream to hydrophobic solvent stream (e.g., hexane) is 50:1.

[0042] The mixed solvent stream 166 contains a mixture of hydrophobicsolvent (e.g., hexane) and solvent extractant (e.g., TBP), and these canbe separated by distillation in an evaporator 170. The hydrophobicsolvent 167 separated by this distillation evaporation can be returnedto the liquid-liquid stripper unit 165, and the solvent extractant 171recycled to the extraction unit 140.

[0043] The aqueous stream 168 from the stripper 165, can be evaporated190 to produce the product 1,3-propanediol 193. Optionally ion exchangetreatment 180 using, for example, a mixed bed column with a mixture ofstrong acid cation and strong base anion resins can be used, eitherbefore or after the evaporation stage 190, in order to remove color andsome organic acids such as levulinic acid, as a further purification.Preferably the purity of the 1,3-propanediol 193 can be over 99% byweight, and a high yield of 1,3-propanediol is possible using thisprocess.

[0044] Recovery of 1,3-propanediol from a complex aqueous feed (e.g.,fermentation broth) in the present invention can result in the selectivetransfer of 1,3-propanediol to a solvent extractant phase. In certainembodiments, the solvent extraction of the present invention can be usedto separate a few, specific impurities along with PDO from a complexaqueous feed stream comprising PDO and impurities. Certain contaminants,which can be present in an aqueous feed (e.g., fermentation broth)comprising PDO are chemicals of the same chemical class as PDO (e.g.,low molecular weight hydroxylated compounds). Contaminants that are inthe same class as PDO, with logP in the range of—2.1 to 1 are forexample glycerol, butanetriol, or glucose. (See examples in the tablebelow.) glycerol −2.08 1,4 butanediol −1.384 1,2 PDO −1.003 ethanol−0.24

[0045] Compounds in the class of low molecular weight hydroxylatedcompounds, such as PDO, tend to interact strongly with water, and areoften completely miscible with water. Methods known in the art canrequire high energy input (e.g., in distillation) to separate water fromthese compounds, as these compounds interact strongly with water and aremiscible with water. Thus, the fact that 1,3-propanediol and relatedcompounds can be recovered in a water-immiscible solvent, as in thepresent invention is surprising. It is even more surprising that the PDOcan be selectively extracted over compounds of the same class. Thus,selective extraction of PDO from aqueous feed into water-insoluble(e.g., castor oil) or low-miscibility (e.g., TBP and hexanol, amongothers) solvents as in present invention was unexpected.

[0046] The following examples are included to demonstrate preferredembodiments of the invention. It should be appreciated by those of skillin the art that the techniques disclosed in the examples which followrepresent techniques discovered by the inventor to function well in thepractice of the invention, and thus can be considered to constitutepreferred modes for its practice. However, those of skill in the artshould, in light of the present disclosure, appreciate that many changescan be made in the specific embodiments which are disclosed and stillobtain a like or similar result without departing from the spirit andscope of the invention.

EXAMPLE 1 Single Stage Extractions and Back Extractions of1,3-propanediol

[0047] Example 1a. Extraction with Tributyl Phosphate 4.2 ml of aconcentrated aqueous fermentation broth containing 31.33% w/v1,3-propanediol (PDO), 1.66% Glycerol, 0.74% 1,2,4 butanetriol (BTO) and0.13% glucose was thoroughly mixed with 35 ml of tributyl phosphate(containing 6% water) at 20° C. The mixture was separated with the aidof centrifugation into two phases (37 ml of Light 1 phase (e.g., firstphase) and 2.5 ml of Heavy 1 phase (e.g., second phase)). The Light 1phase comprising the tributyl phosphate (4 ml) was purified by mixingwith 0.24 ml of water and allowed to separate to give a Heavy 2 phasecomprising water (0.3 ml) and a “purified” Light 2 phase comprisingtributyl phosphate (3.7 ml).

[0048] Example 1b. Back Extraction with Water

[0049] The purified Light 2 phase comprising tributyl phosphate (3 ml)was back extracted with 11.5 ml of water by mixing and separating thephases, to give Light 3 phase comprising tributyl phosphate (3 ml) andHeavy 3 phase comprising water (11.5 ml).

[0050] Example 1c. Back Extraction with Hexane

[0051] 2 ml of the purified Light 3 phase was back extracted withn-hexane (6 ml) by mixing and separating the phases to give Light 4phase comprising hexane (5.8 ml) and Heavy 4 phase comprising water (0.2ml). Table 1 shows the compositions of the streams encountered in thisexample. TABLE 1 Phase Composition % w/v % Purity PDO Glycerol BTOGlucose PDO Feed Broth 31.33 1.66 0.74 0.13 92.6 Extraction with TBPLight 1 2.38 0.06 0.04 0.00 96 Heavy 1 16.06 1.81 0.75 0.05 Purificationwith water Light 2 1.67 0.03 0.01 0.00 97.4 Heavy 2 10.77 0.50 0.25 0.02Back extraction with water Light 3 0.06 0.00 0.00 0.00 Heavy 3 0.46 0.010.00 0.00 97.3 Back extraction with hexane Light 4 0.26 0.00 0.00 0.00Heavy 4 8.5 0.26 0.15 0.00 96.3

[0052] The color of the fermentation broth fed to the extractions wasbrown. The first extraction gave a light yellow Light 1 phase, and abrown Heavy 1 phase. In the purification stage further color was removedfrom the Light 1 phase as shown by a darker yellow color of the Heavy 2phase.

EXAMPLE 2 Change in Temperature During Extraction of 1,3-propanediol

[0053] 1,3-Propanediol (PDO) can be purified by extracting in hexanol,separating and then cooling the light solvent phase, and then separatingthe heavy aqueous phase that forms. Purer 1,3-propanediol will bepresent in this aqueous phase.

[0054] 3 g of a mixture at 30% of dry solids, containing 1,3-propanediolto be purified and with a composition as in the table below wasextracted in two stages at 90° C. The amount of fresh hexanol used ineach stage was 12 g. The light phase from the second extraction was thenused to extract PDO from 3 g of further 30% dry solids feed in a thirdextraction. The extractions and separations were all carried out inconical glass tubes of approximately 50 ml volume.

[0055] Each extraction was carried out for 20 minutes with periodicagitation. The light phase from the first extraction was discarded.

[0056] The analysis of the light phase for the third extraction is givenin the table below. This light phase is then cooled to room temperatureof 25° C. On cooling it splits to two phases and the newly formedaqueous heavy phase is separated, analyzed, and the results are in thetable. TABLE 2 Light Phase Heavy Phase Feed 90° C. 25° C. SelectivityPDO GLY GLU PDO GLY GLU PDO GLY GLU GLY/PDO GLU/PDO 24.2 1.86 0.46 6.030.16 0.00 28.3 1.69 0.03 1.3 18

EXAMPLE 3 Cross Current Extractions of PDO

[0057] Example 3a. Extraction with Anhydrous Tributyl Phospate

[0058] In a two stage cross-current extraction scheme, 5.0 g of anaqueous feed at 44 % dry solids with the composition (% w/w on drysolids) 91.9% PDO, 6.9% glycerol and 1.2% glucose was thoroughly mixedat ambient temperature with 24.9 g of anhydrous tributyl phosphate(TBP). After settling and centrifugation two clear phases were obtained(27.9 g of a first light phase comprising TBP and 2.0 g of intermediateheavy phase comprising water). The heavy phase was re-mixed with 14 g ofanhydrous TBP and separated to give 15.4 g of a second light phasecomprising TBP and 0.6 g of a final heavy phase comprising water. 98% ofthe original PDO was found in the combined light phases at a purity of93.6%, along with 83% of the original glycerol and 37% of the originalglucose. TABLE 3 Component Phase Weights Composition % w/w PDO Glyc GlucPDO Glyc Gluc % DS Feed 2.009 0.150 0.027 91.9% 6.9% 1.2% 43.7% Light 11.594 0.073 0.004 95.4% 4.4% 0.2% 6.0% Light 2 0.376 0.052 0.006 86.7%11.9% 1.4% 2.8% Heavy 2 0.040 0.025 0.017 48.5% 30.8% 20.8% 13.9% Totallights 1.970 0.125 0.010 93.6% 5.9% 0.5%

[0059] Example 3b. Extraction with Hexanol at 90° C.

[0060] In a two stage cross-current extraction scheme, 6.0 g of anaqueous feed at 29.1 % dry solids with the composition (% w/w on drysolids) 90.7% PDO, 7.3% glycerol and 2.0% glucose was thoroughly mixedat 90° C. with 18.1 g of hexan-1-ol. After settling and centrifugationtwo clear phases were obtained (22.1 g of a first light phase comprisinghexan-1-ol and 2.0 g of intermediate heavy phase comprising water). Theheavy phase was re-mixed with 9.96 g of hexanol and separated to give11.3 g of a second light phase comprising hexanol and 0.7 g of a finalheavy phase comprising water. 97% of the original PDO was found in thecombined light phases, along with 75% of the original glycerol and 21%of the original glucose. The purity of the combined light phases was93.7% (raised from a feed purity of 90.7%) TABLE 4 Component PhaseWeights Composition % w/w PDO Glyc Gluc PDO Glyc Gluc % DS Feed 1.5840.127 0.035 90.7% 7.3% 2.0% 29.1% Light 1 1.261 0.058 0.003 95.4% 4.4%0.2% 6.0% Light 2 0.275 0.038 0.004 86.7% 11.9% 1.4% 2.8% Heavy 2 0.0480.031 0.027 44.8% 29.4% 25.7% 15.2% Total lights 1.536 0.096 0.008 93.7%5.8% 0.5%

EXAMPLE 4 Counter Current Extraction of PDO

[0061] Example 4a. Robatel Extraction with Broth, IncorporatingPurification step

[0062] A laboratory version of a Robatel (an automated sequence ofmixer-settlers) was used having 8 mixer-settler stages operating in acounter current fashion in the extraction step and similarly 8 stages inthe purification step. FIG. 9 is a representative schematic of thegeneral process used. A fermentation broth 64 is added to a combinedfeed 66. The combined feed 66 is mixed with solvent extractant 72 in aprimary extractor (e.g., Robatel mixer settler) 68. The second phase 70(e.g., raffinate) comprising water and impurities (e.g., sugars from thefermentation broth) is removed. The first phase 62 comprising solventextractant and 1,3-propanediol is then washed in a purificationextractor 58. The wash stream 54 that is added to the removed firstphase 62 can be aqueous, either water or water with the addition of washchemicals, for example a base such as sodium hydroxide. The purificationextractor 58 comprises 8 stages as explained above. The aqueous washphase 60 can be recovered from the purification extractor 58 leaving apurified extract 56 comprising solvent extractant and purified1,3-propanediol. The washing or purification with the water 54 canincrease the purity of the 1,3-propanediol by removing some impurities,and the aqueous stream comprising water and impurities is combined withfermentation broth 64 in the combined feed 66 and sent back to the mainextractor unit 68 in order to reclaim any 1,3-propanediol in the aqueouswash 60, and prevent loss of 1,3-propanediol yield.

[0063] The extraction was conducted at ambient temperature. Each stagehad a settler volume of 140 ml. The feed was a fermentation broth 64 atabout 33% dry solids (d.s.) containing 30.17% w/v of PDO, 1.6% glycerol,0.7% 1,2,4 butanetriol (BTO) and 0.1% glucose as well as salts ofsodium, potassium, calcium & magnesium. The cations totaled 4126 ppm.The broth 64 was fed to the system at 0.85 ml/minute where it was mixedwith 0.70 ml/min of purification aqueous outlet stream 60 to give thecombined feed 66 at 1.55 ml /min to the extraction step 68. In theextraction step 68 the combined feed 66 was contacted with 14.0 ml/minof wet TBP (tributyl phosphate) 72 (containing 5.4% water). The outputsfrom the extraction step were a second phase raffinate 70 at 1.1 ml/minand a first phase extract 62 (solvent phase) at 14.45 ml/min. The firstphase 62 was contacted with 0.6 ml/min water 54 in the purificationstage 58, leading to a purification aqueous outlet stream 60 (led backto the extraction step 68) and 14.35 ml/min of purified extract 56(solvent phase). The analyses are shown in the tables below. The yieldof PDO (in the purified extract) was 95% and the purity had been raisedfrom 92.8 to 97.2%. The input of cations was 3200 microgram/minute, withthe purified extract representing 255 microgram/minute. TABLE 5 Analysis% w/v Mass Flow g/min Flow PDO Glyc BTO Gluc PDO Glyc BTO Gluc Broth0.85 31.72 1.63 0.71 0.11 0.270 0.014 0.006 0.001 Purified outlet 0.715.58 1.47 0.52 0.05 0.109 0.010 0.004 0.000 Combined Feed 1.55 26.871.54 0.63 1.55 0.416 0.024 0.010 0.001 Raffinate 1.1 0.99 1.64 0.47 1.10.011 0.018 0.005 0.001 Extract 14.45 2.23 0.08 0.02 14.45 0.322 0.0120.002 0.000 Purified 14.35 1.79 0.04 0.01 14.35 0.256 0.006 0.002 0.000Extract

[0064] TABLE 6 % On dry matter basis Flow PDO Glyc BTO Gluc Broth 0.8592.8% 4.8% 2.1% 0.3% Purified outlet 0.7 88.4% 8.3% 2.9% 0.3% CombinedFeed 1.55 92.2% 5.3% 2.2% 0.3% Raffinate 1.1 31.2% 51.8% 14.7% 2.3%Extract 14.45 95.7% 3.6% 0.7% 0.0% Purified 14.35 97.2% 2.1% 0.7% 0.0%Extract

[0065] Example 4b. Aqueous Back Extraction of Robatel Purified Extract

[0066] 16.4 kg of the Purified Extract from Example 4a was mixed with44.5 kg of reverse osmosis quality water. This water extracts the PDOfrom the solvent in to the water phase.

[0067] This water phase was separated and was mixed with hexane toremove any remaining TBP.

[0068] The water phase was then concentrated by evaporation, to produceproduct with a PDO purity of 97.5%. TABLE 7 % on dry matter basis PDOGlyc BTO Gluc Aqueous 97.5% 2.2% 0.208% 0.24% Back Extract

EXAMPLE 5 Solvent Screens

[0069] Example 5a. PDO Mixture with Single Solvents

[0070] 10 g of an aqueous solution containing 46% w/v PDO, 3.5% glyceroland 2.9% glucose was heated to 30° C. and the required solvent added invery small quantities until a cloudiness just began to develop.Additional solvent (about 1 g) was added and thoroughly mixed. Themixture was allowed to settle for 10 minutes and then centrifuged toachieve complete phase separation. The two phases (solvent and aqueous)were analyzed. The table below shows the distribution coefficients ofthe three species (defined as the concentration in the solvent phasedivided by the concentration in the aqueous phase) and the selectivityof extraction of PDO as compared with glycerol (defined as thedistribution coefficient of PDO divided by the distribution coefficientof glycerol). TABLE 8 Distribution Coefficients Selectivity Solvent PDOGlycerol Glucose PDO/Glycerol Oleyl Alcohol 0.038 0.024 0.001 1.60Hexan-1-ol 0.326 0.134 0.029 2.43 Tributyl phosphate 0.203 0.077 0.0162.65 Butan-1-ol Only one liquid phase formed Pentan-1-ol 0.609 0.4170.256 1.46 4-Methyl Pentan-2-one 0.033 0.008 0.001 4.03 isopropylacetate 0.024 0.005 0.001 5.17 Oleic acid 0.009 0.002 0.241 5.23

[0071] Example 5b. Broth with Mixed Solvents

[0072] 5 ml of a fermentation broth at 33.9% dry material, containing31.3% w/v PDO, 1.66% glycerol, 0.74% 1,2,4 butanetriol and 0.13%glucose, was extracted at ambient temperature with (usually) 30 ml of aseries of solvent mixtures. Two phases were obtained which wereseparated and analyzed. TABLE 9 Distribution PDO/ Volumes CoefficientsGlyc PDO Solvent Feed Solvent Light Heavy PDO Glyc BTO Glucose SelectPurity Hexanol/TBP 80/20 5 30 32.5 1.2 0.23 0.03 0.01 0.00 8.8 97.250/50 5 30 33 1.8 0.17 0.03 0.04 0.00 6.1 97.1 Castor Oil/TBP 80/20 5 66.5 4.5 0.01 0.01 0.00 0.00 2.8 98.2 50/50 5 6 7 4 0.07 0.02 0.03 0.004.9 97.7 Pentan-1-ol/Hexane 80/20 5 30 33 2 0.60 0.26 0.26 2.3 50/50 530 33 2 0.09 0.01 0.01 0.00 8.3 98.5 Butan-1-ol/Hexane 80/20 5 30 32.50.9 0.53 0.08 0.02 0.00 6.8 95.0 50/50 5 30 33 2 0.17 0.03 0.00 5.8Pentan-1-ol/Soya oil 80/20 5 30 32 1.2 0.30 0.06 0.00 5.3 50/50 5 30 323 0.08 0.00 0.47 0.00 High 97.7

[0073] As before the table shows the distribution coefficients of thespecies (defined as the concentration in the solvent phase divided bythe concentration in the aqueous phase) and the selectivity ofextraction of PDO as compared with glycerol (defined as the distributioncoefficient of PDO divided by the distribution coefficient of glycerol).In all cases the purity of the extracted PDO is higher than the 92.5% inthe feed. The selectivities of the mixed solvents (PDO/glycerol) areoften higher than the single solvents shown earlier, and the exclusionof glucose by these solvent mixtures is usually very good.

EXAMPLE 6 Removal of Color and Organic Acids with Alkali

[0074] Successive 15 ml portions of a “Purified Extract” (TBP solution)taken from a 15 Robatel counter current extraction and purification of afermentation broth were mixed with increasing amounts of sodiumhydroxide in 1 ml of water. The heavy phases were separated. The colorof the heavy (aqueous) phases increased as more alkali was added andthat of the light phase decreased. (Light phase color was measured asthe absorbance at 300 nm, and heavy phase at 420 nm.) These are shown inthe table below. The organic acid levels in the respective sequence oflight phases were also measured showing the removal of oganic acids asin the table following. TABLE 10 mg Light Heavy NaOH Phase Phase AddedpH Color pH Color 0 3.5 0.124 3.85 0.004 2.25 4.2 0.081 6.26 0.016 3.55.4 0.043 10.2 0.047 5 7.0 0.029 11.6 0.099 10 7.0 0.021 12.4 0.102 207.7 0.02 12.6 0.103 30 7.8 0.02 12.8 0.103 40 7.9 0.03 13.2 0.103

[0075] TABLE 11 mg NaOH Light Phase Properties (Acids in ppm w/v) AddedpH Lactic Levul Acetic Glycolic Succinic 0 3.5 0 139 378.6 11.9 0.8 2.254.2 0 50.3 238.6 11.5 1.3 3.5 5.4 0 14.1 40.7 9.3 1.4 5 7 0 6.4 41.8 1.40.9 10 7 0 9.2 31.7 1.8 0.9 20 7.7 0 9.2 35.2 1.8 1.2 30 7.8 0 5.9 34.11 1.3 40 7.9 0 18.5 82.1 3.3 1.2

EXAMPLE 7 Mixed Bed for Removal of Contaminants

[0076] A purified aqueous PDO stream, as in Example 4 after hexanewashing, was passed over a 60 ml mixed resin bed and collected in 0.5bed volume fractions. The mixed bed composition was Purolite C160 StrongAcid Cation resin and Purolite A510 Strong Base Anion resin mixed in aratio of 1:2 bed volumes. The bed was effective in removing most organicacids as shown in the following table. Levulinic acid was of concern inthe original purified sample as it was felt to contribute to the color.As can be seen from the results, the mixed bed was effective at removingmost trace acids and the solution remained colorless even afterconcentration. The color of the feed and concentrate was measured as theabsorption at 420 nanometers. The feed color was 0.106, and theconcentrate color was zero. TABLE 12 % w/v ppm w/v Fraction PDO GlycerolBTO Glucose Lactic Levul Acetic Glycolic Succinic Feed 21.98 0.2080.2413 0.045 474 37.9 42.2 35.6 244 0.5 BV 11.63 0.130 0.11359 0 0 1.47.4 0 0 1.0 BV 18.79 0.172 0.13388 0 0 1.2 8.1 1.1 0 1.5 BV 21.06 0.2110.17256 0 0 1.2 8.4 0.7 0 2.0 BV 21.57 0.211 0.15508 0 0 1.1 10.9 1.1 02.5 BV 21.46 0.211 0.15732 0 0 1.2 10.2 0.9 0 3.0 BV 21.47 0.212 0.157710 0 1.1 16 1.1 0 3.5 BV 21.58 0.216 0.16117 0 0 1.8 18.2 1.2 0 4.0 BV21.82 0.229 0.1852 0 0 1.5 20.8 1.7 0 Concentrate 82.73 0.784 0.5543 0 04 43 3 0

EXAMPLE 8 Sequential Hexane Extraction

[0077] 8 ml of a light phase prepared by extracting a fermentation brothwith TBP (containing 1.91% w/v of PDO, 0.039% glycerol, 0,085% 1,2,4butanetriol and no detectable glucose) was contacted with successiveportions of n-hexane by mixing, followed by separating the light andheavy phases. After each contact the heavy phases (all about 0.15 ml)were removed before proceeding to the next contact. The analyses of theinitial light, and the successive heavy phases are shown in the tablebelow. The earlier aqueous phases were less pure (in terms of PDO) thanthe feed, and represented 46% of the PDO in the original TBP solution.The aqueous phases from the 4^(th) and 5^(th) extractions were purer interms of PDO than the feed material. TABLE 13 Hexane Total PDO Totaladded hexane PDO Glyc BTO Gluc purity PDO* Feed 1.91 0.04 0.08 0.0093.9% 4 4 15.87 0.82 0.27 0.00 93.5% 16% 4 8 13.13 1.08 0.35 0.02 90.1%28% 8 16 15.35 0.84 0.27 0.00 93.3% 46% 8 24 17.10 0.63 0.23 0.00 95.3%60% 16 40 19.02 0.42 0.20 0.00 96.9% 79%

EXAMPLE 9 Sequential Water Extraction

[0078] 20 ml of a first phase prepared by extracting a fermentationbroth with TBP (containing 1.91% w/v of PDO, 0.039% glycerol, 0,085%1,2,4 butanetriol and no detectable glucose) was contacted with sixsuccessive 2 ml portions of water by mixing, followed by separating thelight and heavy phases. After each contact the heavy phases (all about 2ml) were removed before proceeding to the next contact. The analyses ofthe initial light, and the successive heavy phases are shown in thetable below. The purity of the aqueous phases increase with successiveextractions. TABLE 14 Water Total added water PDO Total (ml) (ml) PDOGlyc BTO Gluc purity PDO* Feed 1.91  0.04  0.08  0.00 93.9% 2 2 8.0830.310 0.193 0.00 94.1% 42.2% 2 4 4.182 0.102 0.107 0.02 95.2% 64.1% 2 62.025 0.010 0.014 0.00 98.8% 74.7% 2 8 0.902 0.002 0.007 0.00 99.0%79.4% 2 10 0.417 0.000 0.004 0.00 99.1% 81.6% 2 12 0.176 0.002 0.0050.00 96.3% 82.5%

EXAMPLE 10

[0079] 5 g of fermentation broth at 55% dry solids PDO, was added to 30g of tributyl phosphate (TBP) containing varying percentages ofkerosene, from 0 to 50%. The mixtures were mixed carefully so as not tocreate micro bubbles and the time taken for phase separation was noted.

[0080] Table 15 shows that the increase in kerosene percentage in theTBP extracting solvent speeds up the phase separation between theaqueous and solvent phases. At 100% TBP extracting solvent the rate is 5minutes for complete separation, at 80% TBP and 20% kerosene it hasdecreased to 3 minutes (a 40% reduction), at 50% TBP and kerosene therate has decreased to 1.5 minutes (a 70% reduction). Table 15 Settlingrates as a function of time at 20° C. for fermentation broth (at 55% drysolids PDO) and TBP/kerosene mixtures at 6 (solvent):1(broth) Ratio TBP100% Time 1 minute Time 5 minute Top & bottom layers Bottom layer clear& reads separate 5 ml on graduated tube Top layer very fine Top layerall clear no visible cloudy approx. 2% bubbles TBP 80% Time 1 minuteTime 3 minute Kerosene 20% Top & bottom layers Bottom layer clear &reads separate 5 ml on graduated tube Top layer very fine Top layer allclear no visible cloudy approx. 1% bubbles TBP 50% Time 1 minute Time1.5 minute Kerosene 50% Top & bottom layers Bottom layer clear & readsseparate 5 ml on graduated tube Top layer very fine Top layer all clearno visible cloudy approx. 1% bubbles

[0081] All of the methods disclosed and claimed herein can be made andexecuted without undue experimentation in light of the presentdisclosure. While the methods of this invention have been described interms of preferred embodiments, it will be apparent to those of skill inthe art that variations may be applied to the methods and in the stepsor in the sequence of steps of the methods described herein withoutdeparting from the concept, spirit and scope of the invention. Morespecifically, it will be apparent that certain agents which are bothchemically related may be substituted for the agents described hereinwhile the same or similar results would be achieved. All such similarsubstitutes and modifications apparent to those skilled in the art aredeemed to be within the spirit, scope and concept of the invention asdefined by the appended claims.

What is claimed is:
 1. A process for the recovery of 1,3-propanediolfrom a fermentation broth comprising 1,3-propanediol, comprising thesteps of: contacting a fermentation broth that comprises water,1,3-propanediol, and at least one contaminant with at least one solventextractant to form a first mixture, and separating the first mixtureinto a first phase and a second phase, wherein the first phase comprisesa majority of the solvent extractant and at least some of the1,3-propanediol that was present in the fermentation broth, and theweight ratio in the first phase of 1,3-propanediol to any onecontaminant present is greater than the weight ratio of 1,3-propanediolto the same contaminant in the fermentation broth prior to thefermentation broth being contacted with the solvent extractant, andwherein the second phase comprises a majority of the water and at leastsome of the contaminant from the fermentation broth.
 2. The process ofclaim 1, further comprising the step of recovering 1,3-propanediol byremoving the first phase from the second phase.
 3. The process of claim2, wherein the removed first phase is contacted with a first quantity ofaqueous solution to form a second mixture, separating the second mixtureinto a third phase and a fourth phase, wherein the third phase comprisesa majority of solvent extractant of the first phase, and wherein thefourth phase comprises 1,3-propanediol and a majority of the firstquantity of aqueous solution, and the weight ratio in the fourth phaseof the 1,3-propanediol to any one contaminant present is greater thanthe weight ratio of 1,3-propanediol to the same contaminant in thefermentation broth prior to the fermentation broth being contacted withthe solvent extractant.
 4. The process of claim 3, further comprisingthe step of recovering 1,3-propanediol by removing the fourth phase fromthe third phase.
 5. The process of claim 4, further comprising recyclingthe recovered third phase such that the solvent extractant comprises therecovered third phase.
 6. The process of claim 4, further comprisingtreating the recovered fourth phase to further purify 1,3-propanediol inthe fourth phase.
 7. The process of claim 4, further comprisingrecycling the fourth phase such that the fermentation broth comprisesthe recovered fourth phase.
 8. The process of claim 3, wherein thevolume ratio of the first quantity of aqueous solution to the firstphase is between about 20:1 and 1:20.
 9. The process of claim 8, whereinthe volume ratio is between about 20:1 and 1:1.
 10. The process of claim8, wherein the volume ratio is about 7:1 to 3:1.
 11. The process ofclaim 2, wherein the removed first phase further comprises at least somewater, and wherein the process further comprises the step of contactingthe removed first phase with at least one hydrophobic solvent to form asecond mixture, separating the second mixture into a third phase and afourth phase, wherein the third phase comprises the majority of both thesolvent extractant and the hydrophobic solvent of the second mixture,wherein the fourth phase comprises 1,3-propanediol and the majority ofthe water of the first phase, and wherein the weight ratio in the fourthphase of 1,3-propanediol to any one contaminant present is greater thanthe weight ratio of 1,3-propanediol to the same contaminant in thefermentation broth prior to the fermentation broth being contacted withthe solvent extractant.
 12. The process of claim 11, wherein the weightratio of the removed first phase to the hydrophobic solvent is betweenabout 4:1 and 1:4.
 13. The process of claim 11, wherein the hydrophobicsolvent is selected from solvents with logP in the range of betweenabout 3.5 and
 10. 14. The process of claim 13, wherein the solvent is analkane having from 6 to 12 carbon atoms.
 15. The process of claim 1,further comprising adjusting the temperature of the first mixture duringthe contacting step such that 1,3-propanediol is more soluble in thesolvent extractant than in the fermentation broth, wherein hexanol isthe solvent extractant; separating the first mixture into the firstphase and the second phase; removing the first phase from the secondphase; adjusting the temperature of the first phase such that a secondmixture is formed; and separating the second mixture into a third phaseand a fourth phase, wherein the third phase comprises a majority of thehexanol from the first phase, and the fourth phase comprises1,3-propanediol; wherein the weight ratio in the fourth phase of1,3-propanediol to any one contaminant present is greater than theweight ratio of 1,3-propanediol to the same contaminant in thefermentation broth prior to the fermentation broth being contacted withthe solvent extractant.
 16. The process of claim 1, wherein thefermentation broth is concentrated to at least about 90 wt % d.s. 17.The process of claim 1, wherein the fermentation broth is partiallypurified.
 18. The process of claim 1, wherein the fermentation broth hasa pH of between about 2 and
 11. 19. The process of claim 1, wherein thefermentation broth has a pH of between about 6 and
 8. 20. The process ofclaim 1, wherein the fermentation broth comprises between about 20 wt %and 80 wt % dry solids.
 21. The process of claim 1, wherein the processis carried out at a temperature between about 20° C. and 90° C.
 22. Theprocess of claim 1, wherein the process is carried out at a temperaturebetween about 25° C. and 35° C.
 23. The process of claim 1, wherein thesolvent extractant is essentially anhydrous.
 24. The process of claim 1,wherein the solvent extractant is saturated with water.
 25. The processof claim 1, wherein the at least one solvent extractant is selected fromthe group consisting of alkanols, ketones, esters, acids, ethers orvegetable oils.
 26. The process of claim 25, wherein the solventextractant is selected from the group consisting of pentanol,propan-1-ol, hexanol, oleyl alcohol, 4-methyl pentan-2-one, isopropylacetate, tributyl phosphate, oleic acid, soya oil, and castor oil. 27.The process of claim 26, wherein the solvent extractant is selected fromthe group consisting of hexanol and tributyl phosphate.
 28. The processof claim 25, wherein the first mixture comprises a phase enhancerselected from the group consisting of aliphatic and aromatichydrocarbons.
 29. The process of claim 28, wherein the phase enhancer isan alkane having between 6 and 10 carbon atoms.
 30. The process of claim1, wherein the solvent extractant comprises carbon and oxygen atoms in aratio of between about 2:1 and 18:1.
 31. The process of claim 30,wherein the solvent extractant comprises carbon and oxygen atoms in aratio of between about 3:1 and 6:1.
 32. The process of claim 1, whereinthe fermentation broth comprises between about 5 wt % to 85 wt % the1,3-propanediol, and further comprises greater than about 10 wt % water,and between about 5 wt % to 70 wt % of one or more contaminants.
 33. Theprocess of claim 1, wherein the contaminant is a compound selected fromthe group consisting of organic acids, organic salts, inorganic salts,carbohydrates, alcohols, proteins, amino acids, and low molecular weighthydroxylated compounds, and mixtures thereof.
 34. The process of claim33, wherein the low molecular weight hydroxylated compound is selectedfrom the group consisting of glycerol, glucose, and butanetriol.
 35. Theprocess of claim 1, wherein the solvent extractant has a logP betweenabout 0.8 and 7.7.
 36. The process of claim 1, wherein the solventextractant has a logP between about 0.8 and 2.9.